Pebble Graphics Development - Function Execution

Evaluating a symbol that represents a function

0:00 - A symbol 'f' bound to the expression 'z + 5' i.e. f(z) = z + 5
0:08 - Evaluating 'f' with 'z' set to '7' i.e. f(7) is 12
0:21 - Evaluating 'f' with 'z' set to '1' i.e. f(1) is 6
0:40 - Using 'f' in a larger expression i.e. f(7) + 6 is 18